1. Field of the Invention
The present invention relates to differential drives for a motor vehicle, and more particularly, relates to an active torque transfer device for use in a vehicle.
2. Description of Related Art
The differential drive is well known in the motor vehicle industry. The differential drive is used in conjunction with the transmission and drive shaft or propeller shaft (prop shaft) to turn the automotive vehicle wheels at different speeds when the vehicle is going around a curve, to differentiate the speed of each wheel individually and to provide the proper amount of torque to each wheel in slipping, turning, or other road to wheel conditions.
In a traditional torque on demand drive train layout of an automotive vehicle there is a primary driven front/rear axle and a secondary driven xe2x80x9chang onxe2x80x9d axle that is connected via a prop shaft or drive shaft and a torque transfer coupling to the primary driven axle. The torque transfer coupling is usually directly in front of the secondary driven axle. The axle differential creates the division of power (or torque) to each side shaft of the axle. The primary driven axle also includes a differential which divides necessary power to the side shaft of each front axle and then the wheels. The division of torque between the front and rear axle is completed by the torque transfer coupling which is a separate unit on the drive train system and requires space for its housing and other related parts. A current state of the art torque transfer coupling for an automotive vehicle is located between the primary and secondary driven axles of the vehicle and, generally consists of a friction clutch pack which is loaded via a ball ramp mechanism. The ball ramp mechanism is engaged by an electric motor. An electronic control unit senses slip conditions of the wheels, monitors current driving conditions of the vehicle and applies a current to the electric motor which will engage the clutch via the ball ramp mechanism and distribute torque to each wheel as necessary.
An active torque transfer system provides maximum flexibility in the distribution of torque between the axles of an all wheel or four wheel drive automotive system. A similar system can be used in applying torque within an axle on a side to side basis between a left rear wheel and a right rear wheel. Other devices currently used in the art for active torque transfer include electromagnetically engaged pilot clutch to drive a ball ramp mechanism. This mechanism loads the main clutch via electromagnetically engaged pilot clutches. Most of the systems use the same ball ramp mechanism but use different engagement mechanisms to engage the ball ramp mechanism to the clutch unit. All of these active torque drive systems are located in a separate housing usually directly in front of the rear (differential in most cases.
Therefore, there is a need in the art for a device to simplify and reduce the weight and required space of an active torque distribution device for use in an automotive vehicle.
One object of the present invention is to provide an improved torque distribution device.
Another object of the present invention is to provide a torque distribution device that includes a clutch pack that runs at axle speed, which will reduce imbalance issues to the transaxle.
Yet a further object of the present invention is to reduce the packaging requirement in the propeller shaft area of the automotive vehicle.
Still another object of the present invention is to provide a differential that does not require a separate oil housing for a clutch pack, but also reduces or minimizes the effort for the bearings and seals.
A further object of the present invention is to reduce the number of interfaces in the drive train while also reducing the weight and cost of the drive train assembly.
Still a further object of the present invention is to integrate within the existing axle housing the engagement mechanism needed to control the torque between the front and rear axles.
Still a further object of the present invention is to combine the front to rear and side to side locking features of a drive train system within one system unit.
To achieve the foregoing objects the differential drive for use on a vehicle includes a rotatably driven differential housing supported in an axle housing. A differential gear set arranged and supported in the differential housing. A torque distribution device adjacent to the differential gear set. The torque distribution device connects one differential side shaft gear with one side shaft. The torque distribution device is arranged to control the torque between a front axle and a rear axle of the automotive vehicle.
One advantage of the present invention is a new and improved torque distribution device for a vehicle.
A further advantage of the present invention is that the torque distribution device uses a clutch pack that runs with axle speed which reduces imbalance issues throughout the transaxle.
A further advantage of the present invention is the reduced packaging requirement in the prop shaft area of the drive train system.
Still a further advantage of the present invention is the inclusion of the clutch pack within the housing of the differential thus requiring no separate oil housing and also reducing the effort for bearings and seals while improving the cooling of the clutch pack.
Another advantage of the present invention is the reduced number of interfaces within the drive train system and the reduced weight and costs of distributing torque to the drive train system.
A further advantage of the present invention is the integration within the axle housing of the engagement mechanism for the torque distribution device.
A further advantage of the present invention is the combination of front to rear and side to side locking control features within one system.
Other objects, features, and advantages of the present invention will become apparent from the subsequent description and appended claims taken in conjunction with the accompanying drawings.